Currently, the electric spray guns on the market have limited functions. While using the spray gun, if the project requires spraying several paints with different concentration and color, then it will require multiple electric spray guns with different functions. It dramatically increases the cost of spraying. It is also inconvenient to use, especially when working high above the ground, as it is inconvenient to carry several electric spray guns. Therefore, a function-integrated spray gun is needed; however, the main differences between electric spray guns with different functions lie within the paint passage, the air passage, and the paint tank. It is almost impossible to achieve the adjustments of paint passage, air passage and paint tank in one spray gun, but since the pumps in the electric spray guns are roughly the same, it is possible to overcome the current electric spray guns' limited functions by switching different paint passages, air passages and paint tanks while having the same pump in one electric paint gun.